Process for burning gaseous fuels



PROCESS FOR BURNING GASEQUS FUELS Charles John Pedersen, Salem, N. J., assignor to E. I. du Pont de Nemonrs and Company, Wilmington, Del., a corporation of Delaware No Drawing. Application August 18, 1954 Serial No. 450,794

4 Claims. (Cl. 48197) This invention relates to a process for burning gaseous fuels used for heating or lighting purposes, and more particularly to providing a combustion catalyst which facilitates the burning of gaseous fuels without the use of excess oxygen normally required.

When a combustible gas is burned in air, it is known that the reaction does not go to completion and give as the final products of the reaction water and carbon dioxide, and this isso even when the amount of oxygen theoretically required to produce complete combustion is used. Ordinarily, carbon monoxide and free carbon are liberated in the burning of gaseous fuels, and con: sequently the full heat of combustion is not obtained. It has long been recognized that soot and smoke formed through incomplete combustion of gaseous hydrocarbon fuels, such as in gas burners, stoves, furnaces, lamps and other combustion apparatus, can result in decreased efliciency, impairment of heat transfer, atmospheric pollution and a general lack in cleanliness in the combustion apparatus and its environment.

While in many cases the introduction of a large excess of oxygen (from air) causes more complete combustion and in most cases prevents the formation of excess carbon, the addition of large excesses of air has the disadvantage that the air used in effecting combustion must be brought to the combustion temperature, and therefore excessive amounts of energy are consumed which could otherwise be put to usefulwork.

It is an object of the present invention to provide. a combustion catalyst for gaseous fuels which, when used in very small amounts in the gaseous fuel, causes marked efiiciency in the combustion of the fuel itself and prevents the formation of free carbon. Itis a further object of the invention to provide a simple and economical process forefiiciently burning gaseous fuelswithout the addition of excessive amounts of air.

I have found that the combustion of gaseous'fuels may be assisted, and the production of carbon ordinarily produced in the burning of these gaseous fuels reduced or eliminated entirely, by having present in'the gaseous fuel or in the air or oxygen employed in its burning a small amount of dicyclopentadienyliron which may be added either as a vapor or in very finely divided solid form. The dicyclopentadienylirons employed are preferably the dicyclopentadienyliron (C H Fe) and its lower molecular weight homologs such as those containing one or two additional carbon atoms in the molecule, which have sufiicient volatility to be readily used with gaseous fuels.

The gaseous fuels may be any of the carbon containing fuels which are gaseous at normal temperatures and pressures (20 C. and 760 mm.) and include natural gas, gases resulting from cracking operations in the pe troleum industry, water gas, etc., or the straight hydrocarbon gases themselves such as methane, ethane, ethylene, acetylene, propane, propylene, methyl acetylene, butane, butylene, butyne, and their isomers, butadiene,

2,867,516 Patented Jan. 6, 1959 diacetylene and C hydrocarbons boiling below 20 C. such as neopentane.

The dicyclopentadienyliron used in this invention is a stable, yellow, crystalline, rather volatile solid melting when pure at from 173 to 174 C. The preparation and properties of the dicyclopentadienyliron are described in U. S. Patent 2,680,756 of June 8, 1954, to Pauso-n. The bis(methylcyclopentadienyl)iron which also comes within the scope of the invention is a somewhat volatile red-brown solid. Its preparation and properties are more particularly described in a. co-pending U. S. patent application Serial No. 352,294 of Graham and Whitman, filed April 30, 1953, and owned by the assignee of the present application. Other iron compounds also coming within the scope of this invention are the cyclopentadienyl(methylcyclopentadienyl)iron, the cyclopentadienyl(ethylcyclopentadienyl)iron, and similar lower alkyl substitution derivatives of the dicyclopentadienyliron itself.

The amount of the iron compound employed may vary widely and will depend upon the nature of the gas being burned, the completeness of combustion desired, the amount of air employed, the type of burning and other conditions of combustion. In some cases it may be desirable to use a lesser amount of the iron compound than required to ensure complete absence of carbon, although the amount usually required to effect complete combustion is small. Usually one part by weight of the dicyclopentadienyliron will be used to from 20 to 2,000 parts by weight of the gaseous fuel, using at least the quantity of oxygen theoretically required for complete combustion of the fuel. In other Words, from 0.05% to 5.0% of the dicyclopentadienyliron compound based on the weight of the gaseous fuel will 'be used. Usually 0.2% will be sufficient to effect complete combustion." on the other hand, amounts in excess of 5% of the weight of the fuel maybe used, although such higher concentrations unnecessarily add to the expense, and when too large an amount of the dicyclopentadienyliron is used objectionable amounts of iron oxide may I result, depending upon the particular type of apparatus used. a

In carrying out this invention the dicyclopentadienyliron is preferably added as a vapor to the gaseous hydrocarbon fuel, although it may also be added to the air or oxygen employed in supporting combustion. This is usually accomplished by heating the air or the fuel and passing it through the dicyclopentadienyliron in granular or crystalline form. In this way the iron compound is vaporized and maintained in the vapor phase. The iron compounds may also be present in the gas as a finely dispersed solid or liquid. Thus, an alternative method for introducing the required amount of the dicyclopentadienyliron is to feed the finely powdered solid continuously at the required rate into a stream of air or gaseous fuel flowing at a rate sufiicient to maintain the solid in suspension or in similar manner adding the liquid compound in atomized form so that it is carried in the stream of air or gaseous fuel to the point of combustion.

When the iron compound is vaporized into the gas phase, the critical factors in determining its concentration in the vapor phase are its temperature, the surface exposed and the rate of gas How. It is usually preferable to work with a gas which is not saturated with respect to the iron compound, since the latter will not then separate if the gas is slightly cooled before burning.

The following examples are given to illustrate the effectiveness of the dicyclopentadienyliron compounds as combustion catalysts in the burning of gaseous fuels.

In these examples the gaseous hydrocarbon was passed '3 through a temperature-controlled tube and burned from the open end of the tube in quiescent room air so as to produce an upright flame of about one inch in height havinga diameter of about one-fourth inch at the out-- let end of the tube. Using the natural gas described below, an appreciable amount of black smoke, which insofar as could be determined visually was not influenced by changing the temperature of the combustible gases over the range from 20 to 86 C., was produced by the flame. When the one-fourth inch tube carrying the combustible gases was packed loosely with the dicyclopentadienyliron compound in crystalline form for a length of six inches and the tube temperature maintained at less than approximately 20 C., the visual smokiness of the flame was essentially equal to the smokiness when the iron compound was not present in the tube; however, when the temperature of the tube was increased, a progressive decrease in the smokiness of the flame occurred due to the increasing amounts of iron compounds which vaporized and were carried into the flame by the combustible hydrocarbon gases. At a particular temperature enough was carried into the burning zone to promote the combustion to such an extent that either very little smoke or no smoke whatsoever was visible. of the quantities of hydrocarbon gases burned and the amounts of iron compound vaporized, the concentrations of the latter necessary to reduce markedly, or to eliminate flame smokiness, were determined.

The following examples illustrate the use of a commercially available gas:

Example 1.Dicycl0pentadienyliron Composition of natural gas by volume:

Percent Propene 36 Propane 26 Air 38 Example 2.Bis(methylcyclopentadienyl) iron The same natural gas was used as in Example 1 and was burned at the same rate. The bis (methylcyclopentadienyl)iron used was in liquid form. When heated to 100 C. in the gas stream, smokiness was entirely eliminated from the flame. One part of this iron compound was vaporized for about 500 parts of the hydrocarbon.

From measurements Similar increased efiiciency in the burning of other gaseous fuels results by the use of the dicyclopentadienyliron compounds as above described.

I claim:

1. A process for reducing the smoking tendencies of a flame produced in the combustion of gaseous hydrocarbon fuels with oxygen, which comprises incorporating into the gaseous fuel-oxygen mixture 1 part by weight of a volatilizable dicyclopentadienyliron compound per 20 to 2000 parts by weight. of the gaseous fuel, the amount of oxygen employed being at least that theoretically required to effect complete combustion of the fuel.

2. A process for reducing the smoking tendencies of a flame produced in the combustion of gaseous hydrocarbon fuels with oxygen, which comprises incorporating in the gaseous hydrocarbon fuel 1 part by weight of a volatilizable dicyclopentadienyliron compound per 20 to 2000 parts by weight of the gaseous fuel, the amount of oxygen employed beingat least that theoretically required to effect complete combustion of the fuel.

3. A process for reducing the smoking tendencies of a flame produced in the combustion of gaseous hydrocarbon fuels with oxygen, which comprises incorporating in the gaseous hydrocarbon fuel 1 part by weight of dicyclopentadienyliron per 20 to 2000 parts by weight of the gaseous fuel, the amount of oxygen employed being at least that theoretically required to effect complete combustion of the fuel.

4. A process for reducing the smoking tendencies of a flame produced in the combustion of gaseous hydrocarbon fuels with oxygen, which comprises incorporating in the gaseous hydrocarbon fuel 1 part by weight of his (methylcyclopentadienyl)iron per 20 to 2000 parts by weight of the gaseous fuel, the amount of oxygen employed being at least that theoretically required to effect complete. combustion of the fuel.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Yant et al.: J. Am. Chem. Soc.,' 49, 1454-1460 (1927).

Charlot: Compt. Read, 194, 374-6 (1932). 

1. A PROCESS FOR REDUCING THE SMOKING TENDENCIES OF A FLAME PRODUCED IN THE COMBUSTION OF GASEOUS HYDROCARBON FUELS WITH OXYGEN, WHICH COMPRISES INCORPORATING INTO THE GASEOUS FUEL-OXYGEN MIXTURE 1 PART BY WEIGHT OF A VOLATILIZABLE DICYCLOPENTADIENYLIRON COMPOUND PER 20 TO 2000 PARTS BY WEIGHT OF THE GASEOUS FUEL, THE AMOUNT OF OXYGEN EMPLOYED BEING AT LEAST THAT THEORETICALLY REQUIRED TO EFFECT COMPLETE COMBUSTION OF THE FUEL. 